1. Field of the Invention
The present invention relates to a semiconductor light emitting device having a light detecting element for detecting emission light and, more particularly, to a semiconductor light emitting device suitable for use in which light detection precision is highly desired.
2. Description of the Related Art
In a semiconductor light emitting device for use of an optical fiber, an optical disk, or the like as a related art, as part of a purpose of maintaining the light output level of a semiconductor light emitting element which is assembled in the device, light emitted from the semiconductor light emitting element is detected by a light detecting mechanism. The light detecting mechanism may be constructed by, for example, a reflector for branching a part of emission light and a semiconductor light detecting element for detecting the branched emission light. The configuration, however, has problems such that the number of parts is large and, in addition, the reflector and the semiconductor light detecting element have to be disposed with high precision with respect to the semiconductor light emitting element. As one of measures to solve such problems, the semiconductor light emitting element and the semiconductor light detecting element are integrally formed.
However, when they are formed integrally, there is the possibility that the semiconductor light detecting element detects not only induced emission light to be detected but also natural emission light. In such a case, the light output level of the semiconductor light emitting element measured on the basis of light detected by the semiconductor light detecting element includes an error only by the amount of natural emission light. Therefore, this method is not also suitable for use in which the light output level is desired to be controlled with high precision.
In Japanese Patent No. 2,877,785, a technique is proposed, of providing a control layer in a semiconductor light detecting element and interrupting light before a part of natural emission light emitted from a surface-emitting semiconductor laser element is detected by the semiconductor light detecting element.